1. Field of the Invention
The present application generally relates to underground conduit inspection. More specifically, the present application relates to an improved underground conduit inspection system utilizing ground-penetrating radar.
2. Description of the Related Art
Ground-penetrating radar (GPR) is a real-time, non-destructive testing technique that can be used to locate targets embedded in concrete and to inspect the interior walls of concrete structures. GPR operates on the principle of transmission, reflection, and detection of short duration electromagnetic pulses from a transducer that is moved across the surface of the structure being analyzed.
GPR utilizes high frequency radio waves that can yield data with very high spatial resolution (e.g., on the order of centimeters) and the data can be acquired rapidly. Data collection can be continuous, allowing scanning of a two-foot by two-foot (60 cm by 60 cm) area in 15 minutes or less, or capturing several kilometers of continuous data in a few hours.
Current applications of GPR for structural engineers most commonly include locating spacing and depth of reinforcing steel, post tensioning cables or anchors, measuring rebar cover, mapping voids, and clearing areas prior to cutting, coring and trenching. GPR can also be a useful tool for seismic upgrades, road and bridge deck condition surveys, mapping delamination, or locating “lost” footings and/or utilities. See, e.g., Csaba Ékes, “Ground Penetrating Radar: Applications of GPR for Non-Destructive Concrete Testing and Structural Investigations,” Construction Business, March/April 2007, pp. 48-49; and “Introduction to GPR,” Terraprobe; “Csaba Ékes, “GPR: A New Tool for Structural Health Monitoring of Infrastructure,” each of which is incorporated in its entirety by reference herein.
Structural applications can include addressing the integrity of the concrete itself, such as the presence of voids, cracks, or chemical alteration. Due to the less well defined character of such features, GPR applicability is not always predictable on these projects and interpretation of the results depends on the specific site conditions and on the experience of the technical personnel. Intrusive testing, such as drilling or coring, often accompanies GPR investigations in order to draw definitive conclusions.